NOVELTY STATEMENT
We have demonstrated that PCNDs carrying cargo proteins achieve
cytosolic protein delivery in an ultrasound-guided manner. To achieve
enhanced therapeutic effects and reduced side effects in protein drug
treatment, an ultrasound-responsive carrier is promising because focused
ultrasound readily penetrates deep into the body in a non-invasive
manner and only a limited region is exposed to ultrasound. For endosomal
escape of cargo proteins, we employed PCNDs as carriers to destabilize
the endosomal membrane via ultrasound-induced vaporization of PCNDs in
endosomes. To date, no protein has been reported to be released from
endosomes by utilizing PCND vaporization. Here, we designed and
synthesized a novel PEG-lipid that can conjugate with any cargo protein
on the lipid coating of the droplets through disulfide bond formation
because it is required that cargo proteins be released from the carrier
in the reductive cytosol. In this study, both cargo proteins with and
without free thiols in their wild type forms were released in the
cytosol in response to ultrasound by utilizing reversible protein
thiolation in the absence of thiol. Thus, our study clearly shows the
proof of a principle that PCNDs are versatile carriers for
ultrasound-guided cytosolic protein delivery.